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f PATN OND DEWEY 0.00m, 0F TE HAUTE,

INDTANA, ASSTGNOE, TO COLUMEIAN ENAMEJLTNG @t STAMPTNG COMPANY, F TERREHAUTE, INDIANA, A COEJPU- TIUN OE TANA.

n werner-n or nn' specification of Letters Patent.

ELEiD W.

Application med April d, 1919. Serial No. Steff.

scription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

'This invention relates to the manufacture of enameled ware and moreparticularly to the production of enameledl ware from sheet steel, orsimilar metal, and to the treatment of the sheet steel as a preliminaryto the Alb enameling operation.

lin the production of enameled ware, the steel is customarily pickled inacid solutions to clean the surface and the enameling is then carriedout as expeditiously as possible to guard against the oxidation of theclean surface; and it has been an axiom of the enameling industry thatthe presence of oXid on the surface of the steel was a condition to bestrenuously guarded against.

rlFhe usual procedure followed in preparing the steel for enameling isbriefly as follows: rThe steel-is received nin the form of rolled sheetsand is pressed or drawn' into the form of culinary or other utensils. Tofacilitate this drawin operation, and to permit the steel to pull reelythrough thedies, an emulsion of mineral oil is applied to the sheet.

After the utensil has been shaped the customary operation is the removalof the oil by scaling. The practice in this operation is to dip the warein an acidbath and while wet with the acid to heat it to redness forseveral minutes. By this treatment the oil is burned 0E, and the coatingof iron oxid which results is in a condition to 'be removed by theaction of a pickling solution. Ur the oil may be removed by scrubbingthe utensil with a soap solution or soap powder or similarldetergent.lln either case it is necessary that the steely be subsequently cleanedby subjecting it to a pickling treatment, that is by immersing it forsometime in an acid solution to remove the oXid. The acid solution isusually a solution of mineral acids, such as sulfuric orl hydrochloricacids, or an acidr enameling operation,

.layer of oXid takes place,

containing solution such as a solution of sodium acid sulfate.

The operations thus commonly employed for the removal of the oil fromthe steel and for the cleaning of the steel are expensive, and theapparatus therefor occupies considerable space. lf the oil is removed byheating, a furnace is necessary for the carrying out of the heatingoperation. rlhe operation of scrubbing with a detergent is likewise anexpensive operation. Where hot pickling liquids are employed, theprovisionof heating means is necessary. The pickling operation consumesconsiderable time, is of a disagreeable character, and requiresconsiderable apparatus and space therefor, the coat of acids and ofsteam for heating forms a very considerable element of expense in theoperation of an enameling plant.

According to the present invention the preliminary treatment of theoiled surface of the sheet steel for the removal of oil, and thesubsequent pickling thereof prior to the are avoided, and the sheetsteel with its oiled surface is subjected to a combined heating andoxidizing operation which leaves the surface of the sheet steel in acondition well adapted for the enameling treatment.

The present invention is based upon the discovery that, contrary to whathas been commonly believed, freedom from oXid of the steel surface to beenameled is not necessary; that the usual operations of cleaning,pickling and washing can be "avoided, that the oil or grease present onthe steel after the drawing operation can be removed, and the steelplaced in condition for the enameling operation, b-y a simple regulatedheatin of the steel ware to the proper degree; an that the resultingsteel ware, which has an oxid coating, is well adapted for use, withoutfurther treatment, in the enameling operation. p

As the result of my investi ations, ll have been led to Ibelieve thatthe ormation of a in the common enameling operation, while the steelwith its enamel coatmg is being heated to the required temperature forthe fusion of the enamel, and that the formation of such an o lid layerunder the enamel is essential to the proper adherence and .smoothness ofthe while enamel; and I have found that the enamelgram'matic manner, ingoperation can be promoted by the formadrawings, in whichtion of a properoxid coating upon the steel v Figure I shows the furnace conventionallyprior to the application 'of the enamelng in side elevation;

composition thereto andthe subsequent i'ir- Fig. 2 is a transversesectional view; and 70 ing operation. v Fig. 3 is an enlarged viewshowing a suit- In the practice of the present invention, able form ofchain conveyer.

the steel ware with its coating of oil is sub- The lire brick tunnel 1is suitably supportjected to a short heating operation at such ed b-ysupports 2 and heated by seiies of a. temperature that the oil will bequickly burners 3. Supported on the staggered volatilized or burned andthe steel will be .Y bricks 4 is a hearth 5 having bearing plates in theaccompanying l oxidized to the desired degree. It has been 6 for thelinks 8 of the chain to which the found that the amount of oxygen takenup cross bars 7 are secured. .The endless chain by the steel, when thusoxidized, 4was about passes yover end rollers or sprockets 9 and 0.0004gram per square centimeter, or that 10, a suitable worm or other drive(not the amount of iron oxid formed wasalbout shown) being provided fordriving the p 0.0014 gram per square centimeter. The sprocket 10. Asupporting or guide rail oxid formation should be such that the steel llis provided for the endless belt on its rehas a pronounced blue color.In general, the turn. Openings for the escape of products vsteel shouldhave as deep a blue color as posof combustion are indicated at l2.

nacel can be similarly increased.

sible, without becoming black. I have ob'- In the operation of theapparatus the tained good results in the practice of the insheet metalware is supported on the cross vention, by carrying out the heatingoperabars 7 or on projections therefrom, and is tion in a gas furnacemaintained at a temcarried through the furnace and there heatperature ofabout 700 C. and by subjecting ed in the manner above described. Asuiii- 90 the steel ware to the temperature of such a cient length ofthe endless chain is provided furnace for a period of about thirtyseconds. at the discharge end of the furnace so that In this time the'steel being treated does not the ware will be cooled before it isfinally reach the temperature of the furnace, and removed. consequentlythe oxidation is not carried as It will be evident that, far as whenYthe steel itself 'becomes red hot. character described, the A di'erenttemperature or time of heating, furnace and of different which willproduce the desired blue oxid be readily regulated. coating, may be usedin place of the particu- The oxidation of the steel should not be larconditions above mentioned. carried too far and the oxid film producedgas red furnace of the leer type has shouldA not become too thick,otherwise it been found well adapted to the practice of will not beentirely absorbed by the molten the invention. I have thus used toadvanenamel during the ,enameling operation. tage a furnace having alire brick tunnel The function of the layer or Hlm of oXid, as 10 feetlong, 30 inches wide and l2 inches I believe, is to provide a mediumthrough 105 high at the center, with the gas burners which the enamel issecured to the steel, so placed below the bottom of the furnace, andthat the com-position of the enamel changes with circulation of thegases therefrom progressively from pure enamel to enamel throughopenings between the bottom and containing increasing quantities of ironsides of the furnace. The burners were so oxid which is united to theunderlying iron arranged that all or any portion of the by means of theiron oxid union. It appears length of the furnace could be heated and tobe essential for substantially all of the were provided with anautomatic constant oxid Y.film to b e absorbed by the molten temperaturecontrol. An endless chain was enamel, in order to obtain a proper unionrun through the furnace over the sprockets of the enamel with the metal.Ground and at each end, so that the ware could be fed in polished crosssections of sheet steel which has been enameled after treatment in thespeed of the chain and the length of the manner above described, whenexamined ina furnace `of the 95 temperature of the parts thereof, can

en pickled before enameling, p e pickling does not, as is sometimes`supposed, yield a surface which is however, be somewhat varied to bringabout rougher and promotes a better union of the the desired oxidation,e., to produce a deep enamel with the steel. blue color. By increasingthe length of the From the above description it will be seen furnace andcorrespondingly increasing the that the process of the present inventionspeed of the chain, the capacity of the furavoids the/necessity for theusual cleaning and pickli'ng treatment, that the burning furnace of thecharacter above referred olf and'removal of grease and other foreign tois illustrated, 1n a conventlonal and diamatter from the steel ware canbe effected 130 by the same operation which results in the formation ofan oXid coating, and that by the heating of the steel ware to the properdegree an oxid coating is formed to which the enamel coating can beapplied directly without. any preliminary pickling operation. rl`heoptimum quantity of oxid that has been found desirable can be developedby the regulated heat treatment which is also suflicient to completelyvolatilize or burn the oil present on the steel, and the steel, aftersuch treatment, can be enameled directly without further preparation,and with the resulting production of an enamel comparable in quality toan enamel whichhas been applied to pickled steel.

The enameling operation itself, to which the oxidized steel issubjected, may be the customary enameling operation to which pickled canbe carried out in the usual way, z'. e., by'

applying the enamel to the oxidized surface, drying and firing.

ll claim 1. rllhe method of making enameled ware, which comprisessubjecting sheet steel having an oil coating thereon to a regulatedheating to remove the oil and form a blue oXid coating thereon, andsubjecting the resulting oxidized steel to an enameling operation,whereby preliminary treatment of the oiled surface for the removal vofoil and subsequent pickling thereof prior to the? enameling operationare avoided.

2. rllhe method of producing enameled ware, which comprises subjectingsheet steel having an oil coating thereon to a drawing operation toshape, heating the ware to remove the oil and produce a thin oXidcoating thereon, applying the enameling composition to the oxidizedsurface, and firing the resulting ware, whereby preliminary treatment ofthe oiled surface for the removal of oil and subsequent ,picklingthereof prior to the enameling operation are avoided.

3. The method of enameling steel ware havingy an oil coating thereon,which comprises subjecting the ware to a temperature of about 700o C.for about 30 seconds to steel isj subjected, and this operationproduceware of the desired' remove the oil and produce an r oxidized surface,and subjecting the resulting oXidized ware to an enameling operation,whereby preliminary treatment of the oiled surface for the removal ofoil and subsequent pickling thereof prior to the enameling operation areavoided.

a. The method of enameling steel ware having an oil coating thereon,which comprises continuously passinq the ware through a furnace, heatedto afbout 700 C., at .such a rate that the ware will be subjected tosuch temtperature for a period of about 30 seconds, and thereby removingthe oil and producing a thin oxid coating, and subjecting the resultingware to an enameling operation, whereby preliminary treatment of theoiled surface for the removal of oil and subsequent pickling thereofprior to the enameling operation are avoided.

5. The method of preparing steel, iron and like metal surfaces forenameling which comprises subjecting such surfaces having an oil coatingthereon to a regulated heating operation sufficient to removeV the oiland form a blue o-Xid coating thereon, whereby preliminary treatment ofthe oiled surface for the removal of oil and subsequent pick'lingthereof prior to the enameling operation are avoided.

6. The method of preparing sheet metal ware for enameling whichcomprises subjectirlg sheet metal having an oil coating thereon to adrawing operation to produce ware of the desiredshape andheating thedrawn ware to remove the oil and produce a thin oXid coating thereon,whereby preliminary treatment of the oiled surface for the removal ofoil and subsequent pickling thereof prior to the enameling operation areavoided.

7. The method of preparing sheetrrnetal ware for enameling whichcomprises subjecting the ware to a temperature of about 700 C. for about30 producing an oxidized surface adapted to receive the enamelingcomposition.

ln testimony whereof ll aiix ,my signature.

naYMoun nnuur 'ooo-Kn seconds and therebyv

